Rotary impact motor

ABSTRACT

In a rotary impact motor, a tool driving anvil has a circumferential groove forming an axial cam rise. The rotary hammer carries an impact dog for conjoint rotation. The impact dog is movable axially in the hammer between impact and release positions relative to the anvil. The impact dog is power biased towards the release position and has a follower lug which engages the anvil groove. During relative rotation between the hammer and the anvil the follower lug is forced by the cam rise to move axially against the power bias to deliver a rotational impact against an impact surface in the anvil groove.

United States Patent Schoeps et al.

[ July 11, 1972 [54] ROTARY IMPACT MOTOR [72] inventors: Knut Chrktian Schoeps, Nacka; Kim

Johan Astrom, Danderyd, both of Sweden [30] Foreign Application Priority Data Jan. I4, 1970 Sweden ..421

[52] US. Cl. ..l73/93, 81/523 [51 Int. (I 325d 15/00 [58] Field ofSearch ..l73/93, 93.6; 81/523 3,272,265 9/ l 966 Schrader et al 173/93 3,331,452 7/1967 Wanner 1 73/93 3,001,428 9/1961 Sindelar 1 73/936 3,001,429 9/1961 Sindelar 1 73/936 Primary Examiner-James A. Leppink Attorney-Bauer and Goodman [57] ABSTRACT in a rotary impact motor, a tool driving anvil has a circumferential groove forming an axial cam rise. The rotary hammer carries an impact dog for conjoint rotation. The impact dog is movable axially in the hammer between impact and release positions relative to the anvil. The impact dog is power biased towards the release position and has a follower lug which engages the anvil groove. During relative rotation between the hammer and the anvil the follower lug is forced by the cam rise to move axially against the power bias to deliver a rotational impact against an impact surface in the anvil groove.

l0Claims,12Drawingfigures ROTARY IMPACT MOTOR This invention relates to a rotary impact motor of the type incorporating a rotatable anvil, a hammer rotatably supported in coaxial relation to the anvil, and an impact dog guided for conjoined rotation on the hammer, the impact dog being axially movably arranged relative to the hammer and the anvil for taking respectively impact and release positions therebetween under the action of respectively cam means engageable with the impact dog and a power bias acting thereon.

In such impact motors the effective cooperation between the cam means and the impact dog is vital if good impact action is to be attained. Prior solutions display considerable complicity as to shape and construction of the impact dog, the anvil, the hammer, and the cam means, or of all these elements simultaneously, which tends to increase undesirably the price of impact wrenches and other tools incorporating the rotary impact motors in question.

It is therefore the main object of the invention to provide in the aforementioned type of rotary impact motors a simplified design as to shape and combination of the main parts incorporated therein. Another object of the invention is to provide in such a combination an increased rigidity in the joumalling and cooperation of the parts involved. A further object is to eliminate power bias providing springs in the arrangement of the impact dog and to substitute them for a simple and dependable cam mechanism.

SUMMARY OF THE INVENTION For the above and other purposes there is according to the invention provided a rotary impact motor comprising a housing, an anvil rotatably supported in said housing, a hammer rotatably journalled in said housing in coaxial relation around said anvil, means in said housing for rotating said hammer, a peripheral groove on and circumferentially around said anvil, an impact surface in said groove, an impact dog axially movably but non-rotatably supported in said hammer for taking respectively impact and release positions relative to said impact surface, a radially inwardly directed follower lug on said impact dog in engagement with said groove, said groove providing an axial cam rise for moving, during relative movement between said hammer and said anvil, said follower lug to impact position against said impact surface, and means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position.

The above and other purposes of the invention will become obvious from the following description and from the accompanying drawings in which two embodiments of the invention are illustrated by way of example. It should be understood that these embodiments are only illustrative of the invention and that various modifications thereof may be made within the scope of the claims following hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings FIG. 1 is a longitudinal section through the rotary impact motor according to the invention with the impact dog in the release position.

FIG. 2 is a section on the line 22 in FIG. 1.

FIG. 3 is an enlarged partial side view of the anvil in FIG. 1.

FIG. 4 is a view of the impact dog seen radially from the inside in FIG. 1.

FIG. 5 is a side view made partly in section of a driving element included in FIG. 1.

FIG. 6 is a fragmentary section on an enlarged scale seen on the line 6-6 in FIG. 1.

FIGS. 7-9 show partly in section diagrammatic functional views of the main parts of the rotary impact motor. In more detail, FIG. 7 shows a plane development of the hammer, the impact dog, and the driving element of the rotary impact motor at the instant of impact with the impact dog in an impact position. FIG. 8 shows the details in FIG. 7 immediately after the impact with the impact dog in a released position. FIG. 9 shows the details in FIG. 7 prior to impact.

FIGS. 10-12 show partly in section diagrammatic functional views of the main parts in a modified embodiment of the rotary impact motor according to the invention. In more detail, FIG. 10 shows a plane development of the hammer, the impact dog, and the driving element of the rotary impact motor at the instant of impact with the impact dog in an impact position. FIG. 11 shows the details in FIG. 10 immediately after the impact with the impact dog in a released position. FIG. 12 finally shows the details in FIG. 10 immediately after impact.

In the figures the rotary impact motor is shown as forming part of a motor driven impact tool 15, and more particularly a hand sustained impact action nut setter. In a housing 16 the impact tool 15 comprises a conventional motor, not shown in the figures, for example a reversible pneumatic vane motor which rotates a drive shaft 17. The impact motor proper is mounted between the housing 16 and a front piece 18 which rotatably supports a projecting anvil 19. The anvil 19 has a square end 20 intended for carrying removable tools such as, for example, a socket wrench.

The drive shaft 17 has a splined portion 22 which is in engagement with a cooperating inwardly splined portion 23 in a driving element 24. The driving element 24 is a cylindrical body can-led by the drive shaft 17 having a bore 25 which rotatably supports a rear end pivot 26 on the anvil 19. Between the end pivot 26 and the drive shaft 17 a centering pin 27 is received in axial bores. Around the centering pin 27 a spacing washer 28 provides an abutment between the splined portion 23 and the end pivot 26. The anvil 19 is supported rotatably in a joumalling sleeve 21 provided with a rear radial flange and carried by the front piece 18. The anvil 19 has an enlarged middle portion 29 of equal diameter with the driving element 24. In the middle portion 29 is formed a peripherally surrounding helical or screw groove 30. The opposite transverse end walls of the screw groove 30 are designated respectively by 31 and 32, FIGS. 3 and 9, and provide impact surfaces extending obliquely outwardly in a nearly radial direction in the middle portion 29 of the anvil 19. The end portions of the screw groove 30 adjacent the impact surfaces 31, 32 are arranged in overlapping arrangement and open one into the other axially. As is evident from FIG. 3, the flanks or axial sides of the screw groove 30 provide an axial cam rise in the extension of which the impact surfaces 31, 32 are disposed at the end portions of the thread groove.

A tubular hammer 34 is rotatably supported by the outer cylindrical surfaces of the driving element 24 and the middle portion 29 and is kept axially in place around these parts between a rear flange 35 on the driving element 24 and the radial flange of the joumalling sleeve 21. The tubular hammer 34 is provided with an inner axial recess or groove 36 which in cross section has a dove-tail shape. In the axial groove 36 is slidably journalled an elongated impact dog 37 which by a dove-tail shaped base portion is received in and is slidably guided by the axial groove 36. The impact dog 37 has forwardly thereof a radially inwardly directed follower lug 40 which is trapeziforrn in longitudinal section and by its axial flanks 44, 45 slidably cooperates with the flanks of the screw groove 30. The follower lug 40 is wedge-shaped in cross section. The impact dog 37 with the wedge flanks of the follower lug 40 can either take an impact position in engagement with one of the impact surfaces 31, 32 on the middle portion 29 or take a release position at either entrance into the screw groove 30, as for example in FIG. 8 at the rear entrance.

For creating a power bias capable to move the impact dog 37 to a release position, a spring, not shown, may be compressed between suitable abutments on the impact dog 37 and the driving element 24. More advantageous, however, is to provide the driving element 24 with a canted groove 41 in which is received a ball 42 in its turn inserted into a semispherical recess 39 fixedly at the rear end of the impact dog 37. As a result, control of the impact dog 37 function is carried out entirely without springs.

Let it be supposed that the square end 20 by meanS of a socket wrench, not shown, is connected to a nut to be screwed onto a fastener means having a right hand thread. The bidirectionally rotatable motor of the tool 15 is set for rotation in the clockwise direction when viewed in the direction of the arrows 2-2 in FIG. 1 and upon starting the drive shah 17 will transmit rotation to the driving element 24 and the oblique groove 41 which applies the driving torque against the ball 42 and thus against the semispherical recess 39 and the impact dog 37. The impact dog 37, in turn, is at the base portion thereof bound to rotate conjointly with the hammer 34 which followingly also starts rotating. While the nut is screwed down, the rotational resistance is small and the rotation of the impact dog 37 is transmitted by way of friction via the follower lug 40, which latter is disposed somewhere in the screw groove 30, for example in any of the positions depicted in FIGS. 7-9, on to the middle portion 29 of the anvil and to the square end 20.

Suppose that the frictional driving position is the one shown in FIG. 7. When the nut has been screwed down the rotational resistance willincrease very rapidly and the anvil 19 together with the middle portion 29 thereof will be retarded and stops. The impact dog 37 is driven continuously by the driving element 24 and the oblique groove 41 thereof and strives together with the hammer 34 to go on rotating. Since one wedge flank of the follower lug 40 abuts against the impact surface 31, the impact dog 37 is prevented from rotating. By reason thereof the continued turning of the driving element 24 results in a retraction of the ball 42 in the oblique groove 41 from the position in FIG. 7 to the position illustrated in FIG. 8, whereby the follower lug 40 is retracted from impact position towards the driving element 24 to a release position at the entrance into the screw groove 30. In that position the impact dog 37 and the hammer 34 are again free to rotate since the follower lug 40 now is in the screw groove 30 and by its rear flank 44 slides up onto the cam riseof the thread groove30 following the latter, that is, slides on the rear axial side of the thread groove 30, circumferentially around the arrested middle portion 29 of the anvil 19 in the forward direction away from the driving element 24. Under angular acceleration of the hammer 34 there is successively performed an axial advancin'g of the impact dog 37 in the hammer 34 and of the ball 42in the groove 41, the position in FIG. 9 is rapidly passed and as acceleration is continued, the follower lug 40 will be displaced to the position of FIG. 7 bearing on the impact surface 31 lying in the path of movement thereof and delivering the kinetic energy stored in the hammer 34 and the impact dog 37 by way of a rotational blow against the anvil 19, the square end 20 and on to the nut. Thereuponthe described impact cycle is repeated again and again until the desired tensioning torque has been reached in the nut.

During rotation in the opposite direction the follower lug 40 obviously delivers impacts against the impact surface 32 at the opposite end portion of the screw groove 30. Contrary to what was the case during rotation in the clockwise direction, the power bias applied on the impact body 37 at the oblique groove 41 and the ball 42 will be directed axially away from the driving element 24 while the screw groove 30 with the forward axial side thereof will guidingly support the forward flank 45 of the follower lug 40 and move the latter towards the driving element 24 to an impact position against the impact surface 32.

In the embodiment diagrammatically illustrated in FIGS. -12, the screw groove 30 has been substituted for by a peripheral ring groove 46 comprising at the rear axial side or flank 55 thereof an axial cam crest 49 bordered by doublesided cam surfaces 47, 48. The driving element 24 is provided with a V-shaped ball groove 50 for cooperation with the ball 42 of the impact dog 37, as a result of which the impact dog 37 always will be subjected to a power bias in the direction axially towards the driving element 24 regardless of the rotational direction. The impact dog 37 has a follower lug 51 provided with a rearwardly directed cam crest 52 bordered by doublesided cam surfaces and adapted for cooperation with the flank 55 of the ring groove 46 and the cam crest 49 of the latter. In a straight line extension of the cam surfaces 47 and 48, respectively, the ring groove 46 presents at the forward axial side or flank 56 thereof angularly spaced impact surfaces 53, 54 against which the impact dog 37 with the side flanks of the follower lug 51 is arranged to deliver impacts. The cam crest 49 is disposed intermediately relative to the impact surfaces 53, 54.

Suppose that the anvil 19 and the middle portion 29 thereof during tightening of a screw has stopped in the position illustrated in FIG. 10. Continued rotation of the driving element 24 entrains the impact dog 37 to a release position towards the cam surface 47, FIG. 11, by the aid of the branch of the ball groove 50 trailing in the rotational direction. The hammer 34 is thereupon accelerated together with the impact dog 37 circumferentially around the middle portion 29 of the anvil while the cam crest 52 by way of the ball groove 50 is forced to follow the flank 55. The cam crest 52 of the follower lug 51 thereupon runs up with high rotational velocity onto the cam surface 48, FIG. 12, passes the latter and throws up the follower lug 51 against the impact surface 54, FIG. 10. The impact cycle is thereupon repeated until the nut has been set tight. During rotation in the opposite direction the cam crest 52 at the impact delivering instant evidently will run up onto the cam surface 47 and the follower lug 51 will deliver impacts against the impact surface 53.

What we claim is:

l. A rotary impact motor comprising:

a housing;

an anvil rotatably supported in said housing;

a hammer rotatably joumalled in said housing in coaxial relation around said anvil; means in said housing for rotating said hammer;

a peripheral groove on and circumferentially around said anvil;

an impact surface fonned in said groove;

an impact dogaxially movably but-non-rotatably supported in said hammer for taking respectively impact and release positions relative to said impact surface;

a radially inwardly directed follower lug on said impact dog in engagement with said groove;

an axial cam rise formed in said groove for moving, during relative movement between said hammer and said anvil, said follower lug to an impact position against said impact surface; and

means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position.

2. A rotary impact motor according to claim 1 in which said groove is a screw groove, the end portions of which open into one another axially, said end portions each being terminated by an impact surface transverse to said groove.

3. A rotary impact motor according to claim 2 in which said follower lug has opposed flank surfaces engageable with said screw groove and is wedge shaped in a direction parallel to said flank surfaces.

4. A rotary impact motor accordinG to claim 1 in which said impact dog is dove-tail shaped in cross section at the base portion thereof and wherein said hammer has a groove therein of corresponding dove-tail cross-section, said impact dog being axially slidably guided in said hammer groove.

5. A rotary impact motor according to claim 1 in which said groove is a ring groove provided with said cam rise which includes a cam crest bordered by double-sided cam surfaces.

6. A rotary impact motor according to claim 5 in which said follower lug has an axial cam follower crest bordered by dou ble-sided cam surfaces which cooperates with the cam crest of said ring groove to move said follower lug to said impact position.

7. A rotary impact motor according to claim I in which said rotating means is a driving element rotatably supported in said housing, said power bias means including a cam mechanism between said driving element and said impact dog.

8. A rotary impact motor according to claim 7 in which said cam mechanism includes an axially canted groove on said driving element and a ball carried on said impact dog for cooperative engagement with said canted groove.

9. A reversibly rotatable impact motor comprising:

a housing;

an anvil rotatably supported in said housing;

a tubular hammer rotatably journalled in said housing in coaxial relation around said anvil, said hammer having an internal axial groove therein;

means in said housing for rotating said hammer bidirectionally;

a circumferential screw groove on said anvil with the end portions of said screw groove in axial communication with one another and each end portion being terminated by an impact surface transverse to said screw groove;

an impact dog axially movably supported in said axial hammer groove for taking respectively impact and release positions relative to said impact surfaces at said axial communication of said screw groove end portions;

a radially inwardly directed follower lug on said impact dog in engagement with said screw groove for being moved by said screw groove during relative movement between said hammer and said anvil to an impact position against said impact surfaces; and

means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position. 10. A reversibly rotatable impact motor comprising:

a housing;

an anvil rotatably supported in said housing;

a tubular hammer rotatably joumalled in said housing in coaxial relation around said anvil, said hammer having an internal axial groove therein;

means in said housing for rotating said hammer bidirectionally;

a circumferential ring groove on said anvil;

opposed impact surfaces transverse to said ring groove at one axial side thereof, and an axial cam crest bordered by double-sided cam surfaces at the other axial side of said ring groove and disposed intermediate said impact surfaces;

an impact dog axially movably supported in said axial hammer groove for taking respectively impact and release positions relative to said impact surfaces when adjacent thereto;

a radially inwardly directed follower lug on said impact dog in engagement with said other axial side of said ring groove, said cam crest in said ring groove providing an axial cam rise for moving, during relative movement between said hammer and said anvil, said follower lug to an impact position against said impact surfaces; and

means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position. 

1. A rotary impact motor comprising: a housing; an anvil rotatably supported in said housing; a hammer rotatably journalled in said housing in coaxial relation around said anvil; means in said housing for rotating said hammer; a peripheral groove on and circumferentially around said anvil; an impact surface formed in said groove; an impact dog axially movably but-non-rotatably supported in said hammer for taking respectively impact and release positions relative to said impact surface; a radially inwardly directed follower lug on said impact dog in engagement with said groove; an axial cam rise formed in said groove for moving, during relative movement between said hammer and said aNvil, said follower lug to an impact position against said impact surface; and means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position.
 2. A rotary impact motor according to claim 1 in which said groove is a screw groove, the end portions of which open into one another axially, said end portions each being terminated by an impact surface transverse to said groove.
 3. A rotary impact motor according to claim 2 in which said follower lug has opposed flank surfaces engageable with said screw groove and is wedge shaped in a direction parallel to said flank surfaces.
 4. A rotary impact motor according to claim 1 in which said impact dog is dove-tail shaped in cross section at the base portion thereof and wherein said hammer has a groove therein of corresponding dove-tail cross-section, said impact dog being axially slidably guided in said hammer groove.
 5. A rotary impact motor according to claim 1 in which said groove is a ring groove provided with said cam rise which includes a cam crest bordered by double-sided cam surfaces.
 6. A rotary impact motor according to claim 5 in which said follower lug has an axial cam follower crest bordered by double-sided cam surfaces which cooperates with the cam crest of said ring groove to move said follower lug to said impact position.
 7. A rotary impact motor according to claim 1 in which said rotating means is a driving element rotatably supported in said housing, said power bias means including a cam mechanism between said driving element and said impact dog.
 8. A rotary impact motor according to claim 7 in which said cam mechanism includes an axially canted groove on said driving element and a ball carried on said impact dog for cooperative engagement with said canted groove.
 9. A reversibly rotatable impact motor comprising: a housing; an anvil rotatably supported in said housing; a tubular hammer rotatably journalled in said housing in coaxial relation around said anvil, said hammer having an internal axial groove therein; means in said housing for rotating said hammer bi-directionally; a circumferential screw groove on said anvil with the end portions of said screw groove in axial communication with one another and each end portion being terminated by an impact surface transverse to said screw groove; an impact dog axially movably supported in said axial hammer groove for taking respectively impact and release positions relative to said impact surfaces at said axial communication of said screw groove end portions; a radially inwardly directed follower lug on said impact dog in engagement with said screw groove for being moved by said screw groove during relative movement between said hammer and said anvil to an impact position against said impact surfaces; and means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position.
 10. A reversibly rotatable impact motor comprising: a housing; an anvil rotatably supported in said housing; a tubular hammer rotatably journalled in said housing in coaxial relation around said anvil, said hammer having an internal axial groove therein; means in said housing for rotating said hammer bi-directionally; a circumferential ring groove on said anvil; opposed impact surfaces transverse to said ring groove at one axial side thereof, and an axial cam crest bordered by double-sided cam surfaces at the other axial side of said ring groove and disposed intermediate said impact surfaces; an impact dog axially movably supported in said axial hammer groove for taking respectively impact and release positions relative to said impact surfaces when adjacent thereto; a radially inwardly directed follower lug on said impact dog in engagement with said other axial side of said ring groove, said cam crest in said ring groove providing an axial cam rise for moving, during relative movement betwEen said hammer and said anvil, said follower lug to an impact position against said impact surfaces; and means in said housing for providing an axial power bias on said impact dog for moving said impact dog to said release position. 